As shown in FIGS. 8 and 9, a known guide, in the form of a tensioner lever 500, is composed of a synthetic resin shoe 510 having integrally molded, L-shaped engagement pieces 511, which engage one side of a shoe-supporting base 520, and a plurality of strip-shaped engagement pieces 512, which engage the opposite side of the base, to prevent the floating of the shoe 510 relative to the base 520. The guide is used to guide, and maintain proper tension in, a transmission chain. Such a guide is described in U.S. Pat. No. 5,184,983, granted Feb. 9, 1993.
Another known guide is shown in FIGS. 10 and 11. In this guide 600, a plurality of L-shaped engagement pieces 613, and a plurality of strip-shaped pieces 614, are integrally molded as parts of a synthetic resin shoe. The engagement pieces are disposed in a zigzag arrangement along the length of the shoe, with three L-shaped pieces situated on one side of the shoe, and two strip-shaped pieces and one L-shaped piece on the other side of the shoe, the last-mentioned L-shaped piece being adjacent one end of the shoe. Such a guide is described in United States Patent Publication 2006/0205548, published Sep. 14, 2006.
The guide 500 in FIGS. 8 and 9 has a simple engagement structure in which one side of the shoe has only strip-shaped engagement pieces. Consequently, the shoe is liable to become disengaged from the supporting base while in operation. A clearance is provided between the synthetic resin shoe and the arm to allow for expansion and contraction of the resin. Expansion and contraction is repeated due to a changes in temperature in the engine in which the guide is used, and can result in longitudinal movement of the shoe sufficient to cause the shoe to disengage the supporting base.
In the guide shown in FIGS. 10 and 11, the dimensional tolerances are strictly set in order to avoid clearances between the base frame and the L-shaped and strip-shaped engagement pieces in the assembled guide. However, in order to maintain these strict tolerances, manufacture of the guide requires troublesome high precision molding of the shoe. Moreover, if strict dimensional tolerances are not maintained in the manufacture of the shoe, a widthwise shift of the shoe relative to the base frame can occur when the shoe is in sliding contact with a traveling transmission chain, generating biased wear, which sometimes results in premature breakage of the shoe.
This invention provides a guide which avoids the above-described problems. The invention also facilitates guide production, and increases the useful life of metal molds used to manufacture the guide, by relaxation of dimensional tolerances. Clearance between the synthetic resin shoe and the base frame is removed, so that, during the use of the guide biased wear of the synthetic resin shoe due to shifts in its mounting position are avoided, the formation of traveling lines is suppressed, and vibration noise due to backlash is also prevented.